1. Field of the Invention
The present invention relates to abutments for dental prostheses implanted in the jawbone of a dental patient. More particularly, the invention provides an abutment post having grooves formed therein for carrying away fluids which would otherwise interfere with successful bonding of a restoration on the abutment post.
2. Description of the Prior Art
Replacement of lost teeth by prostheses individually anchored in the jaw has become a popular procedure. A complete prosthesis assembly includes an implant or anchor which is implanted in the jaw and becomes osseointegrated with bone tissue, an abutment which is received and supported within the implant, and a crown or restoration which simulates a natural tooth. The crown or restoration is typically cast from a suitable metallic alloy over the abutment, and is supported on the abutment. The crown or restoration typically has a porcelain or other ceramic coating for esthetic purposes. In a successful implant, only the restoration is visible, except for a plug which is visible from the top of the prosthesis. The plug closes a hole formed in the restoration for enabling a screw employed to secure the restoration to the implant. The screw passes through a hole formed in the restoration, and engages threads formed in the implant.
A successful implant and associated implant, if properly fabricated, will usually last for the life of the patient if properly fabricated. However, certain problems can arise from poorly fabricated restorations. One example is metal bubbles formed at abutting surfaces of the abutment and the restoration. Such bubbles can form when air and other gasses are not vented during casting of the restoration. Bubbles reduce engagement area of the restoration relative to the abutment, cause the abutment not to fit flush to the implant, destabilize the screw joint, and promote loosening of the screw. Another possible fault is thinness of the lowermost wall of the abutment where it covers and encircles the post of the abutment. This wall can spread, thereby losing grip on the abutment. Alternatively, an open area can be created between the restoration and the post of the abutment should the wall distort, thereby promoting growth of undesirable microorganisms in the mouth.
Still another problem which can arise is loss of proper orientation of the restoration with respect to the abutment. One example is withdrawal of the restoration from the abutment, illustratively where the former pulls free from the latter. In this case, the restoration could be swallowed or otherwise lost. Still another example is rotation of the restoration about the post of the abutment. This will result in angular misalignment of the prosthesis within the mouth, which could cause inability of the jaws to fully close, an objectionable esthetic situation, and a feeling of discomfort to the patient.
U.S. Pat. No. 4,988,298, issued to Richard J. Lazzara et al. on Jan. 29, 1991, illustrates an abutment having horizontal, circumferential grooves formed therein. In one embodiment, the present invention differs from the device of Lazzara et al. in having generally semi-elliptical grooves rather than the horizontal, circumferential grooves of Lazzara et al., and also in that the abutment has negative taper. Alternatively stated, the post of the abutment is tapered such that it is wider at the top or free end than it is at the bottom or base where it engages the implant. The groove of the present invention, when projected onto a sectional plane of the abutment, extends in both horizontal and vertical orthogonal axes as it encircles the abutment.
U.S. Pat. No. 5,820,374, issued to William F. Simmons et al. on Oct. 13, 1998, illustrates a dental implant having a textured exterior surface to improve osseointegration. The implant is not an abutment having either negative taper or grooves which extend in two orthogonal axes.
U.S. Pat. No. 5,897,320, issued to Neal B. Gittleman on Apr. 27, 1999, illustrates an abutment having relief channels formed therein to conduct excess dental cement away when cementing a prosthesis to an abutment. The channels include a vertical channel and a horizontal channel. Gittleman modifies the post of the abutment to receive the vertical channel and to accept a plug. By contrast, the generally frustoconical surface of the abutment post is not modified in the present invention other than by the groove itself, whereas Gittleman provides machined flat surfaces. This is difficult to fabricate, since a typical abutment is less than one quarter inch (six mm) in diameter.
Also, the plug of Gittleman must be very precisely formed to cooperate with its associated abutment. In the present invention, no such precision is necessary, since the groove may be formed on the exterior surface of the abutment post. The groove is preferably semi-elliptical in the present invention, and does not have a purely vertical channel and a purely horizontal channel, as taught by Gittleman. Also, the post of the present invention has negative taper in that it is wider at the top of the abutment than it is at the bottom of the abutment where the abutment contacts the implant. This feature is not shown in Gittleman.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.